Not Applicable
Not Applicable
1. Field of Invention
This invention relates to the field of reconstructing existing bridges and highways, specifically to methods of restoring structural integrity of existing roadways.
2. Prior Art
There are more and more vehicles that use existing transportation infrastructure every year. Due to a drastic increase in traffic load and volume, this aging infrastructure is rapidly deteriorating. At the same time, especially in urban areas, construction of new transportation facilities is severely restricted by environmental regulations, high costs, and existing land development. Therefore, reconstructing existing bridges and highways in order to restore their structural integrity very often remains the only choice available.
Several prior art methods of reconstructing existing roadways in order to restore their structural integrity are well known. One of the methods involves closing an existing roadway to traffic while detouring traffic onto alternative roadways. However, detours are not always possible and, when they are, traffic would spill over onto adjacent roadways, creating traffic jams and safety hazards resulting in increased air pollution, costly disruption of local businesses, and interference with local traffic.
Other methods utilize slowly advancing moveable elevated roadways that provide a travel path for existing traffic, while existing roadway restoration work is performed underneath. They are described in U.S. Pat. Nos. 1,924,779 to B. H. Flynn (1933), 3,811,147 to R. C. Dix (1974), 4,698,866 to H. Kano (1987), 5,042,957 to M. Arita et al (1991), 5,105,494 to D. C. Ogg (1992), German Patents DE2653515 to G. Albersinger (1978), DE3107408 to H. R. Baser (1982), and British Patent GB2227268 to H. R. Fish (1990). Some of these moveable roadways provide an overpass with a single travel lane. They are designed for easier transport from site to site, however, in order to restore an entire width of an existing roadway, these moveable roadways have to make several passes over the same portion of the existing roadway. Other moveable roadways cover an entire width of an existing roadway, which can be restored in a single pass. But, due to their size, they are expensive to transport from site to site and require significant assembly and disassembly, which disrupt existing traffic. Also, due to significant additional weight that these devices impose on an underlying existing structure, their use on bridges is extremely limited.
Another method involves closing at least one of the existing roadway travel lanes to traffic for duration of its restoration, while traffic is rerouted onto those travel lanes that remain open. When restoration of the closed lane is completed, and the lane is reopened to traffic, the same procedure is then repeated for other existing travel lanes, resulting in restoration of the entire roadway. This method, however, is infrequently used because the existing travel lanes that remain open to traffic need to accommodate traffic from the closed lane. This can only take place on an existing roadway that has an overabundance of traffic capacity, which is a rare occurrence, especially in urban areas.
Therefore, if none of the previously described prior art methods can be utilized, which is currently the case on most existing bridges and highways, then a travel lane is closed to traffic for a relatively short duration of time, usually during night hours, and construction equipment, materials and personnel are moved to a roadway restoration area prior to start of restoration work. A relatively small area of the closed lane is then restored overnight, in sub-standard conditions and in a rushed manner. Construction equipment, materials and personnel are then removed from the restoration area prior to re-opening the previously closed travel lane in time for the next period of peak traffic, usually by early morning. As a result, the restoration work sometimes takes years to complete, quality of workmanship suffers, cost of restoration becomes excessive, and useful life of the roadway is shortened.
The previous discussion demonstrates that disruption of existing traffic due to inadequate traffic capacity of existing bridges and highways is the major reason why restoring structural integrity of existing roadways continuously remains one of the most frequently encountered problems in the field.
Transportation authorities, such as Federal, State, and Municipal Departments of Transportation, and public and private transportation agencies, that govern existing bridges and highways, recognize the problem of traffic disruption that occurs during restoration of existing roadways. And since traffic volumes on existing roadways vary significantly between peak and off-peak traffic, the authorities issue regulations that specify when and how many of existing travel lanes shall be open to traffic, and when and how many of them may be closed with minimal disruption of existing traffic. Generally, all travel lanes of existing roadways are required to be open during periods of peak traffic, from early morning to late afternoon, but a predetermined number of travel lanes are allowed to be closed during periods of off-peak traffic, mostly during night hours, with minimal disruption of existing traffic.
The aforementioned regulations provide a window of opportunity for developing methods of reconstructing existing roadways in order to restore their structural integrity with minimal disruption of traffic. Conceptually such a method would involve first increasing traffic capacity of an existing roadway by erecting a new elevated roadway above an existing roadway with minimal disruption of traffic, then rerouting existing traffic from the existing roadway onto the new elevated roadway, and then restoring structural integrity of the existing roadway with minimal disruption of existing traffic.
Prior art has not yet successfully developed such methods, and as a result, many existing bridges and highways, especially in urban areas, suffer from structural deficiencies for many years.
A novel method of reconstructing existing roadways in order to restore their structural integrity with minimal disruption of traffic is provided. In accordance with this method roadway reconstructing is performed in two consecutive stages. During the first stage (Stage A), a new elevated roadway, which comprises a predetermined number of interconnected ramp units and bridging units, is erected above an existing roadway with minimal disruption of existing traffic. This new elevated roadway increases traffic capacity of the existing roadway by providing elevated travel lanes. During the second stage (Stage B), existing traffic is rerouted from the existing roadway onto the new elevated roadway, thus enabling restoration of structural integrity of the existing roadway to be performed with minimal disruption of existing traffic. This method is easily adapted for use on different types of bridges and highways.
Structural deterioration of existing roadways is one of the most frequently encountered problems in the field of reconstructing existing bridges and highways. The primary object of the present invention is to provide a novel, simple and economical solution that enables restoring structural integrity of existing roadways with minimal disruption of existing traffic. This object is accomplished by developing methods and utilizing devices that, working synergistically, offer a complete realization of the task.
Accordingly, a highly efficient method of reconstructing existing roadways in order to restore their structural integrity with minimal disruption of existing traffic is provided. This novel method of reconstructing comprises:
Stage Axe2x80x94erecting a new elevated roadway above an existing roadway with minimal disruption of existing traffic as described below, and
Stage Bxe2x80x94rerouting existing traffic from the existing roadway onto the new elevated roadway, and then restoring structural integrity of the existing roadway with minimal disruption of existing traffic.
During Stage A of reconstructing, in accordance with the preferred embodiment of this method, a new elevated roadway, comprising a predetermined number of interconnected ramp units and bridging units, is erected in multiple steps, mostly during periods of off-peak traffic, and, after completion of each step, it is opened to existing traffic in time for the next period of peak traffic.
The initial step of erecting the new elevated roadway involves erecting at least two entrance/exit ramp units, at least one of which is made moveable. The ramp units are positioned so that an uppermost end of one ramp unit faces an uppermost end of another ramp unit and, when erection of the ramp units is completed, they embody an initial portion of the new elevated roadway that may be opened to traffic, if specified by a transportation authority.
The next step, which is executed during a period of off-peak traffic as specified by the transportation authority, involves closing the previously erected portion of the elevated roadway to existing traffic and creating a gap in the previously erected portion of the elevated roadway by moving the moveable ramp unit along the existing roadway. A bridging unit is then erected in the gap and the moveable ramp is moved back, if necessary, to adjoin the bridging unit. Consequently, an extended portion of the elevated roadway is erected, and it is opened to existing traffic in time for the next period of peak traffic as specified by the transportation authority.
The step of closing a previously erected portion of the elevated roadway to existing traffic during a period of off-peak traffic as specified by the transportation authority, creating a gap in the previously erected portion of the elevated roadway by moving the moveable ramp unit along the existing roadway, erecting a bridging unit in the gap, and opening an extended portion of the elevated roadway to existing traffic in time for the next period of peak traffic as specified by the transportation authority is repeated many times until erection of the predetermined number of the bridging units is completed.
Thus, Stage A of reconstructing is performed with minimal disruption of existing traffic, because, at each step, the previously erected portion of the elevated roadway is open to existing traffic during periods of peak traffic, and it is closed to existing traffic during periods of off-peak traffic.
During Stage B of reconstructing, following completion of erecting the new elevated roadway, structural integrity of the existing roadway is restored in a small number of steps with minimal disruption of existing traffic. Each step involves closing a predetermined number of existing travel lanes to existing traffic, rerouting existing traffic from the closed travel lanes onto the new elevated roadway, restoring structural integrity of the existing travel lanes closed to traffic and rerouting existing traffic back onto the existing travel lanes that have been restored. The step is repeated, if necessary, until the entire roadway restoration is completed with minimal disruption of existing traffic.
Accordingly, both stages of reconstructing the existing roadway are performed with minimal disruption of existing traffic.
Another major object of this invention is to shorten duration of reconstructing existing roadways. During Stage A of reconstructing this object is achieved by utilizing space underneath previously erected portion of elevated roadway to store construction and safety equipment and materials, and to house construction field offices and staging areas, thereby saving time usually required to move these items and personnel to and from work areas.
This object is also achieved by utilizing the space underneath a moveable ramp unit for performing erecting work during periods of peak traffic. This work may include, for example, preparing an existing roadway for coming erection of bridging units or surveying condition of existing load-carrying structural members of the existing roadway. This work is time-consuming and complex, especially when performed at night, however, when the space underneath the moveable ramp unit is utilized, the work is conducted during day-time, while existing peak traffic flows overhead. As a result the quality of workmanship is improved and erecting work is continuously conducted during periods of peak traffic and periods of off-peak traffic, thereby shortening overall duration of construction.
During Stage B of reconstructing this object is achieved by closing existing travel lanes to existing traffic for the duration of their restoration so that the restoration work is performed continuously during periods of peak traffic and periods of off-peak traffic.
This object is further achieved by minimizing a number of different temporary traffic patterns during restoration, and by keeping the established traffic patterns during periods of peak traffic and periods of off-peak traffic.
Still another object of this invention is to make it versatile enough to be used on different types of existing bridges and highways. This object is achieved by minimizing dead load applied to these existing structures by utilizing various light-weight structural forms and materials for new elevated roadways and for restoration work.
Bridging units and ramp units are composed of individual structural members such as deck panels, stringers, braces, and of main frames consisting of columns and floor-beams. The main frames, usually of T, double-T (TT), or portal types, are generally oriented transversely to the direction of traffic, and they serve to support other structural members. The main frames and other structural members may be made of steel, aluminum, other light-weight alloys, or fiber reinforced composite materials in order to minimize their weight, which is especially important when elevated roadways are erected over existing bridges.
Similarly, light-weight forms and materials may be introduced during restoration of deteriorated existing structural members, for example, concrete traffic barriers may be replaced by much lighter aluminum barriers or concrete roadway decks may be replaced by steel orthotropic decks.
This object is also achieved by reducing the live load applied to new elevated roadways as well as to existing roadways. This live load reduction is realized by restricting elevated roadway traffic to xe2x80x9cpassenger cars onlyxe2x80x9d traffic and by restricting existing roadway truck traffic to a minimal number of existing travel lanes as specified by the transportation authority. Since a per-lane live load imposed by truck traffic is several times higher than a per-lane live load imposed by xe2x80x9cpassenger cars onlyxe2x80x9d traffic, it is possible to erect a new elevated roadway carrying several additional xe2x80x9cpassenger cars onlyxe2x80x9d travel lanes without overloading an existing structure.
Another object of this invention is to achieve a higher level of safety for workers and motorists during reconstruction of existing roadways, as well as for motorists after the reconstruction is completed. This object is accomplished by adding a sufficient number of new travel lanes, therefore reducing congestion and upgrading Level-Of-Service.
A higher level of safety is also achieved by allowing xe2x80x9cpassenger cars onlyxe2x80x9d traffic on new elevated roadways, thus separating car and truck traffic. Also, natural lines of separating truck and xe2x80x9cpassenger cars onlyxe2x80x9d traffic are provided on the existing roadways by lines of columns of main frames protected by traffic barriers.
Safety is also improved because construction equipment, materials and personnel need not be moved often to and from work areas, and the workers are protected from traffic by construction traffic barriers.
Safety for traveling public is also increased during Stage B of reconstructing because a number of different temporary traffic patterns are minimized and the established traffic patterns are utilized during periods of peak and off-peak traffic, helping drivers adapt quickly.
Furthermore, a separate travel lane designated for xe2x80x9cemergency vehicles onlyxe2x80x9d may be integrated as a safety feature as well.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the following examples and accompanying drawings.